Passage 9.18.3
ἑξῆς δέ ἐστι τῶν Οἰδίποδος παίδων μνήματα· καὶ τὰ ἐπʼ αὐτοῖς δρώμενα οὐ θεασάμενος πιστὰ ὅμως ὑπείληφα εἶναι. φασὶ γὰρ καὶ ἄλλοις οἱ Θηβαῖοι τῶν καλουμένων ἡρώων καὶ τοῖς παισὶν ἐναγίζειν τοῖς Οἰδίποδος· τούτοις δὲ ἐναγιζόντων αὐτῶν τὴν φλόγα, ὡσαύτως δὲ καὶ τὸν ἀπʼ αὐτῆς καπνὸν διχῇ διίστασθαι. ἐμὲ δὲ ἐπηγάγοντο ὧν λέγουσιν ἐς πίστιν ἰδόντα ἄλλο τοιόνδε.
Next come the tombs of the children of Oedipus. Although I have not witnessed myself what is performed upon them, I nevertheless consider the reports reliable. For the Thebans say that they make offerings both to other heroes who are considered such and to the children of Oedipus. And when they offer sacrifices to these, the flame, and likewise the smoke arising from it, divides itself into two parts. Something else I saw convinced me of the truth of what they say.